Uncompyle6

====================

- Pypy 3.3, 3.5, 3.6, and 3.6.9 support
- bump xdis version to handle newer Python releases, e.g. 2.7.17, 3.5.8, and 3.5.9
- Improve 3.0 decompilation
- no parse errors on stlib bytecode. However accurate translation in
control-flow and and/or detection needs work
- Remove extraneous iter() in "for" of list comprehension Fixes 272
- "for" block without a `POP_BLOCK `and confusing `JUMP_BACK` for `CONTINUE`. Fixes 293
- Fix unmarshal incompletness detected in Pypy 3.6
- Miscellaneous bugs fixed

=================================

- Fix fragment bugs
* missing `RETURN_LAST` introduced when adding transformation layer
* more parent entries on tokens
- Preliminary support for decompiling Python 1.0, 1.1, 1.2, and 1.6
* Newer _xdis_ version needed

================

- Correct assert{,2} transforms Fixes 289
- Fragment parsing fixes:
* Wasn't handling 3-arg `%p`
* fielding error in `code_deparse()`
- Use newer _xdis_ to better track Python 3.8.0

=======================

The main change is to add a tree-transformation phase. This simplifies the
code a little and allows us to turn `if ...: raise AssertionError` into
`assert`, and many `if ..: else if ...` into `if ... elif ..`

Use options `--show=before` and `--show=after` to see the before the tree transformation phase and after the tree transformation phase.

Most of the heavy lifting for this was done by x0ret.

Other changes:

- Fix issue 275, 283 (process to fix this bug is documented on wiki), 284
- blacken more code
- CircleCI adjustments for a changing CircleCi
- Require more recent `xdis` for Python 3.8
- Fix bugs in code using `BUILD_LIST_UNPACK` and variants